1. Field of Invention
This invention relates to generating encryption keys at both the originating and terminating terminals of a wireless network, and particularly the generation of the same encryption key at both terminals.
2. Description of Related Art
To secure private communications between devices over public frequency bands, signals are generally encrypted. While numerous cryptographic methods exist, authentication of the devices and distribution of authentication keys to prevent theft of the key has been a problem.
One method for authentication has been the challenge/response protocol based on a private key cryptographic algorithm. An individual subscriber unit (ISU) is issued a secret key, such as an authentication key (A-key), which is known only to the ISU and the service provider control center. The A-key is a cryptographic key variable stored in the memory of an ISU, and is generally entered into the ISU memory once when the ISU is first put into service. The A-key remains unchanged unless it is determined by a user or service provider that the value of the A-key has been compromised. Intermediate ISU cryptovariables, known as shared secret data (SSD), are generated from the unique and private ISU A-key.
Most private key encryption techniques, such as Data Encryption Standard (DES) use keys, such as the A-key, generated at a central location. The keys are distributed over the airwaves to ISUs. However, the distribution of keys over the airwaves offers an interloper the opportunity to obtain the keys and other relevant ISU identification information. The interloper can then program the intercepted information into an imitation ISU, resulting in an imitation ISU impersonating the original ISU. While impersonating an original ISU, the interloper can fraudulently obtain wireless services or retrieve otherwise private voice, data or video communications.
When it has been discovered that the key has been compromised, a new key must be distributed to the compromised ISU. The easiest and fastest way to distribute the new key from the control center is by transmitting the new key over the airwaves which is subject to interlopers, as discussed above. Thus, new technology is required to reduce this risk of interception of the encryption key.